Valve timing within internal combustion engines may be varied to alter performance characteristics and increase efficiency of operation. Some systems use a cam phaser with a first element driven in a fixed relationship to the crankshaft and a second element mounted to the end of the camshaft and adjacent to the first element. In one example, the first element is a stator mounted inside a crankshaft-driven component and having a plurality of radially-disposed inwardly-extending spaced-apart lobes and an axial bore. The second element is a vaned rotor mounted to the end of the camshaft through the stator axial bore and having vanes disposed between the stator lobes to form actuation chambers therebetween such that limited relative rotational motion is possible between the stator and the rotor.
Relative movement between the components of the cam phaser controls the positioning of the camshaft and the valves relative to the crankshaft and the pistons of the engine. In order to efficiently use such a system, the position of the camshaft relative to the crankshaft must be monitored on an ongoing or continuous basis. This sensing of relative position, or cam phase angle sensing, is often determined by monitoring a cam target wheel associated with the second element of the cam phaser to determine the position of the camshaft, monitoring the position of the crankshaft, and comparing their positions to determine the relative angular difference between the camshaft and the crankshaft.
In large engines, tolerance stack-up and torsional issues may impact the accuracy of the relationship between the valves and pistons obtained by monitoring the positions of the camshaft and the crankshaft. Accordingly, it is desirable to increase the accuracy of the cam phase angle sensing without increasing complexity and cost.
The foregoing background discussion is intended solely to aid the reader. It is not intended to limit the innovations described herein nor to limit or expand the prior art discussed. Thus the foregoing discussion should not be taken to indicate that any particular element of a prior system is unsuitable for use with the innovations described herein, nor is it intended to indicate any element, including solving the motivating problem, to be essential in implementing the innovations described herein. The implementations and application of the innovations described herein are defined by the appended claims.